External defibrillators frequently include a pair of “hands-free” disposable electrodes, which are essentially flexible pads that are adhered to the skin of a subject having a cardiac event (i.e., used transcutaneously). The hands-free electrodes can be of the type that are adhered to a subject, rather than paddles that are held by a rescuer during defibrillation. Hands-free disposable electrodes typically include a non-conductive backing layer, a conductive layer, formed from a thin sheet of metal (e.g. tin or silver) or a conductive ink (e.g. silver-chloride) printed on a substrate, and a liquid or solid electrically conductive gel covering the electrically conductive layer so that electrical current passes through the gel to the subject's body. The area of contact between the gel and the subject's body where current is delivered is referred to herein as the “treatment area”.